An occlusion in an elongated body cavity such as in a vessel, especially in an artery, is generally initially widened, in that deposition material, such as plaque is removed by cutting and sucking out or the like. However, this cannot take place up to the tissue material, because at that point an injury risk exists. If merely a narrowing and not a complete occlusion has formed, i.e. a stenosis or a certain through-flow area has been created in the aforementioned manner in the previous complete occlusion, a radial widening of the stenosis is desired. This is carried out not only in blood vessels, but also in other body passages or tubes, such as in the ureter, bile duct, etc.
For this purpose hitherto use has been made of a balloon catheter with a double internal diameter, which brings about an instantaneous radial widening, which is to remain after the catheter has been removed. Permanent widening of such a stenosis is also known. Thus, it has been proposed to axially fix a widening part to such a balloon catheter, insert it with the latter and by widening the balloon catheter to plastically deform the same in such a way that the radial dimensions of the widening part are increased, it is forced into the wall of the stenosis and after the removal of air from the catheter the latter can be removed, whereas the widening part remains in situ in the plastically deformed state. As such a part, e.g. a sleeve in the form of a "helical" envelope has been provided.
A significant disadvantage of the last-mentioned process is that the sleeve can be introduced into the stenosis located on the outer circumference of a catheter. Firstly the axial fixing is complicated and can either not be reliably achieved, so that a part can be left behind on advancing the catheter, or a subsequent release of the part from the catheter is difficult. In addition, damage can result from a widening part externally mounted on a catheter. Finally a widening by the balloon catheter in the case of such a part must lead to a radial extension, which significantly exceeds the ultimately desired radial extension, because such parts, like conventional biocompatible materials, to the extent that they have an adequate strength to keep open a stenosis, have a considerable elastic deformation range, before a permanent plastic deformation occurs to the desired radius. This more particularly applies to a "helically" shaped part of the aforementioned type.